iOS中文件的上传下载功能

iOS开发中会经常用到文件上传下载的功能，这篇文件将介绍一下使用asp.net webservice实现文件上传下载。

首先，让我们看下文件下载。

这里我们下载cnblogs上的一个zip文件。使用NSURLRequest+NSURLConnection可以很方便的实现这个功能。

同步下载文件：

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NSString *urlAsString = @"http://files.cnblogs.com/zhuqil/UIWebViewDemo.zip";
NSURL    *url = [NSURL URLWithString:urlAsString];
NSURLRequest *request = [NSURLRequest requestWithURL:url];
NSError *error = nil;
NSData   *data = [NSURLConnection sendSynchronousRequest:request
returningResponse:nil
error:&error];
/* 下载的数据 */
if (data != nil){
NSLog(@"下载成功");
if ([data writeToFile:@"UIWebViewDemo.zip" atomically:YES]) {
NSLog(@"保存成功.");
}
else
{
NSLog(@"保存失败.");
}
} else {
NSLog(@"%@", error);
}

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异步下载文件：

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(void)viewDidLoad

{

[super viewDidLoad];

//文件地址

NSString *urlAsString = @”http://files.cnblogs.com/zhuqil/UIWebViewDemo.zip“;

NSURL *url = [NSURL URLWithString:urlAsString];

NSURLRequest *request = [NSURLRequest requestWithURL:url];

NSMutableData *data = [[NSMutableData alloc] init];

self.connectionData = data;

[data release];

NSURLConnection *newConnection = [[NSURLConnection alloc]

initWithRequest:request

delegate:self

startImmediately:YES];

self.connection = newConnection;

[newConnection release];

if (self.connection != nil){

NSLog(@”Successfully created the connection”);

} else {

NSLog(@”Could not create the connection”);

}

}

(void) connection:(NSURLConnection *)connection

didFailWithError:(NSError *)error{

NSLog(@”An error happened”);

NSLog(@”%@”, error);

}

(void) connection:(NSURLConnection *)connection

didReceiveData:(NSData *)data{

NSLog(@”Received data”);

[self.connectionData appendData:data];

}

(void) connectionDidFinishLoading

:(NSURLConnection *)connection{

/* 下载的数据 */

NSLog(@"下载成功");
if ([self.connectionData writeToFile:@"UIWebViewDemo.zip" atomically:YES]) {
NSLog(@"保存成功.");
}
else
{
NSLog(@"保存失败.");
}

/* do something with the data here */

}

(void) connection:(NSURLConnection *)connection

didReceiveResponse:(NSURLResponse *)response{

[self.connectionData setLength:0];

}

(void) viewDidUnload{

[super viewDidUnload];

[self.connection cancel];

self.connection = nil;

self.connectionData = nil;

}

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从上面两段代码中可以看到同步与异步下载的区别，大部分时候我们使用异步下载文件。在asp.net webservice中可以将文件的地址返回到iOS系统，iOS系统在去请求下载该文件。

上传文件

我们先使用VB.Net写一个webservice方法，用于接收上传上来的文件数据，代码如下。

?

<WebMethod(Description:="上传文件！")>

_

Public

Function

UploadFile() As

XmlDocument

Dim

doc As

XmlDocument = New

XmlDocument()

Try

Dim

postCollection As

HttpFileCollection = Context.Request.Files

    Dim

aFile As

HttpPostedFile = postCollection(“media”)

aFile.SaveAs(Server.MapPath(".")

+ “/”

Path.GetFileName(aFile.FileName))

doc.LoadXml("<xml>ok</xml>")

Return

doc

Catch

ex As

Exception

doc.LoadXml("<xml>fail</xml>")

Return

doc

End

Try

End

Function

文件上传接口

定义一个类PicOperation用于处理上传图片：

?

@interface

PicOperation : NSOperation

{

UIImage

*theImage;

}

@property

(retain) UIImage *theImage;

@end

[objc] view plain copy

//
//  PicOperation.m
//  DownLoading
//
//  Created by skylin zhu on 11-7-30.
//  Copyright 2011年 mysoft. All rights reserved.
//

#import "PicOperation.h"

#define NOTIFY_AND_LEAVE(X) {[self cleanup:X]; return;}
#define DATA(X) [X dataUsingEncoding:NSUTF8StringEncoding]

// Posting constants
#define IMAGE_CONTENT @"Content-Disposition: form-data; name=\"%@\"; filename=\"image.jpg\"\r\nContent-Type: image/jpeg\r\n\r\n"
#define STRING_CONTENT @"Content-Disposition: form-data; name=\"%@\"\r\n\r\n"
#define MULTIPART @"multipart/form-data; boundary=------------0x0x0x0x0x0x0x0x"

@implementation PicOperation
@synthesize theImage;

//创建postdata
- (NSData*)generateFormDataFromPostDictionary:(NSDictionary*)dict
{
id boundary = @"------------0x0x0x0x0x0x0x0x";
NSArray* keys = [dict allKeys];
NSMutableData* result = [NSMutableData data];

for (int i = 0; i < [keys count]; i++)
{
id value = [dict valueForKey: [keys objectAtIndex:i]];
[result appendData:[[NSString stringWithFormat:@"--%@\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];

if ([value isKindOfClass:[NSData class]])
{
// handle image data
NSString *formstring = [NSString stringWithFormat:IMAGE_CONTENT, [keys objectAtIndex:i]];
[result appendData: DATA(formstring)];
[result appendData:value];
}
else
{
// all non-image fields assumed to be strings
NSString *formstring = [NSString stringWithFormat:STRING_CONTENT, [keys objectAtIndex:i]];
[result appendData: DATA(formstring)];
[result appendData:DATA(value)];
}

NSString *formstring = @"\r\n";
[result appendData:DATA(formstring)];
}

NSString *formstring =[NSString stringWithFormat:@"--%@--\r\n", boundary];
[result appendData:DATA(formstring)];
return result;
}
//上传图片
- (NSString *) UpLoading
{
if (!self.theImage)
NOTIFY_AND_LEAVE(@"Please set image before uploading.");

NSMutableDictionary* post_dict = [[NSMutableDictionary alloc] init];

[post_dict setObject:@"Posted from iPhone" forKey:@"message"];
[post_dict setObject:UIImageJPEGRepresentation(self.theImage, 0.75f) forKey:@"media"];

NSData *postData = [self generateFormDataFromPostDictionary:post_dict];
[post_dict release];

NSString *baseurl = @"http://10.5.23.121:7878/WorkflowService.asmx/UploadFile";
NSURL *url = [NSURL URLWithString:baseurl];
NSMutableURLRequest *urlRequest = [NSMutableURLRequest requestWithURL:url];
if (!urlRequest) NOTIFY_AND_LEAVE(@"Error creating the URL Request");

[urlRequest setHTTPMethod: @"POST"];
[urlRequest setValue:MULTIPART forHTTPHeaderField: @"Content-Type"];
[urlRequest setHTTPBody:postData];

// Submit & retrieve results
NSError *error;
NSURLResponse *response;
NSLog(@"Contacting TwitPic....");
NSData* result = [NSURLConnection sendSynchronousRequest:urlRequest returningResponse:&response error:&error];
if (!result)
{
[self cleanup:[NSString stringWithFormat:@"Submission error: %@", [error localizedDescription]]];
return;
}

// Return results
NSString *outstring = [[[NSString alloc] initWithData:result encoding:NSUTF8StringEncoding] autorelease];
return outstring;
}
@end

这里我主要定义了两个方法，一个是generateFormDataFromPostDictionary用于创建post form data，一个是UpLoading供调用的类上传图片，这个类需要一个UIimage的对象。

类定义好了，上传图片就非常方便了，看下面代码：

[objc] vie
a092
w plain copy

PicOperation *pic = [[PicOperation alloc] init];
pic.theImage=[UIImage imageNamed:@"meinv4.jpg"];;
NSString *result = [pic UpLoading];
NSLog(result);